化学计量学方法来识别选择性离子重叠气相色谱 - 质谱信号的分辨率

1、A chemometric method to identify selective ion for resolution ofoverlapping gas chromatography-mass spectrometry signal(SCIENCE CHINA CHEMISTRY)(May 2013 Vol.56 No.5: 656663)姓名： 李 琴学号：212103019Abstract A chemometric method to determine selective ion by using non-negative immune algorithm (NNIA) was

2、proposed. In the method, the mutual projections of the chromatographic profiles at different m/z channel are calculated using NNIA. Suppose a GC-MS data with m retention time points and n mass channels, the projections of the GC-MS data onto a chromatographic profile at a mass channel will form a ma

3、ss spectrum of 1n vector. If the chromatographic profile at a selective mass channel is used, the extracted mass spectrum will be a correct one. Therefore, by comparing the extracted mass spectrum with a reference spectrum, the selective ion can be identified, and the corresponding chromatographic p

4、rofile can be obtained at the same time. GC-MS data of 40-pesticide mixture was investigated by the method. The results show that both the mass spectral and the chromatographic information of the interested components can be extracted from the overlapping signals, except for the special cases of iso

5、meric components with very similar mass spectra.目录1234IntroductionCalculationExperimentalResults and discussion5Conclusions1. Introduction In this work, NNIA was adopted for the determination ofselective ion in a GC-MS data matrix. In the approach, themutual projection of the chromatographic profile

6、s in an mnGC-MS data matrix is calculated by using NNIA, thus, nextracted mass spectra can be obtained. Among those, thespectrum obtained by the chromatographic profile of theselective ion will be the correct one. Therefore, if a referencemass spectrum is provided for analyzing component,the selecti

7、ve ion can be identified by comparing the extracted mass spectra and the reference one. With the selective ion and the corresponding chromatographic profile, the information of the component can be extracted from thedata matrix.2. Calculation (1) Determination of the reference mass spectrum(2) Calcu

8、lation of the mutual projections(3) Identification of the selective ion(4) Subtraction of the component from the data matrix(5) Repetition(6) Correction and refinement Figure 1 Scheme figure of the proposed method.3. Experimental (1)Data simulation A five-component mixture was simulated for testing

9、theperformance of the method. The GC profiles of the fiveanalytes were simulated by the commonly used exponentially modified Gaussian (EMG) equation , and a constant background with random noise is added as the 6thcomponent. All the mass spectra of the five componentshave 105 m/z channels, each of w

10、hich has at least one selective ion except for the 2nd one, and a mass spectrum is simulated as a background. Therefore, the simulated signal of GC-MS is a 100105 matrix that is obtained by multiplying the six mass spectra and the six chromatographic profiles. (2)Experiment data.GC-MS data of 40-pes

11、ticide mixtures was used for testing the performance of the proposed method. The 40-pesticide mixture was obtained by mixing the standards in a solution with a concentration of 10 mg L-1, as reported in Ref. The sample was analyzed by Thermo GC-MS system consisting of a Trace gas chromatograph with

12、a capillary column of weak polar, CP-Sil8CB (USA, Varian, 30 m long, 0.32 mm i.d., and 0.25 m film thickness) and a Polaris Q mass spectrometry (USA, Thermo Fisher Scientific). The electron impact ionization source (EI) was employed andtuned at 70 eV. The mass range from 50 to 650 mu was scanned. Th

13、e carrier gas was helium (BOC, 99.999%) with a flow rate of 1.0 mL min-1. Furthermore, for speeding upthe analysis regardless of the resolution, a very fast temperature program was used. Therefore, all the components in the mixture are eluted within 12 min, as shown inFigure 2. In this work, the ove

14、rlapping peak clusters in the three regions (4.744.86 min, 5.305.48 min and 5.675.84 min) indicated by the red boxes are selected as examples to investigate the performance of the method.Figure 2 TIC of the pesticide mixture. Three regions enclosed by redboxes are selected as examples to validate th

15、e performance of the method.4. Results and discussion (1)Resolution of the simulated data(a1a5): Simulated. (b1)(b5): Resolved mass spectra before the correction and refinement step. (c1)(c5): Resolved mass spectra after correction and refinement.Resolution of the simulated GC-MS data. (a) Resolved

16、chromatogramsbefore the correction and refinement step, (b) correlation coefficientsobtained for the first component, (c) correlation coefficients obtainedfor the second component, and (d) resolved chromatograms aftercorrection and refinement.(2)Resolution of the experimental GC-MS signals Resolutio

17、n of the experimental GC-MS data. (a) Resolvedchromatograms before the correction and refinement step, (b) correlationcoefficients obtained for the first component, (c)(f) resolved mass spectraof the components before the correction and refinement step.Resolved chromatograms (a) and mass spectra (b)

18、(e) of thecomponents from the first region of the experimental GC-MS data. Resolved chromatograms (a) and mass spectra (b)(e) of thecomponents from the second region of the experimental GC-MS data.Resolved chromatograms (a) and mass spectra (b)(d) of thecomponents from the third region of the experimental GC-MS data. 5. Conclusions A chemometric method to determine selective ion by using NNIA was proposed. With the proposed method, the selective ions of the components in overlapping peaks can be identified, and the information of the interested components can be extracted. Resolu